As a hotel room, it lacked a few essentials. No ensuite, no television, no minibar; I've stayed in better-equipped backpacker's hostels. However, you couldn't fault it for spaciousness. It came with global garden as standard.

More than half a hectare of it in all, carpeted with succulents and sunflowers, hung with bougainvillea and vines, and scattered with date palm, olive and citrus trees. All walled by honeycomb hexagons of plastic pillows arcing away a hundred feet overhead – which, of course, could mean only one place in the world: the Mediterranean biome at the Eden Project in Cornwall. And there – among the undergrowth on the border between South Africa's Fynbos and Karoo, a spit away from the Californian Chaparral of mesquite and sagebrush – sat a romantically dressed double bed.

It was a one-off PR stunt, but a pretty good one. The online hotel booking agency LateRooms.com asked 1,500 customers which normally out-of-bounds British attraction they would most like to stay in. Buckingham Palace and Edinburgh Castle tied at the top of the poll; Sandringham, Balmoral and the Tower of London also figured highly, as did Downing Street, Harrods, Stonehenge, Hadrian's Wall, Blackpool Tower and the Millennium Stadium in Cardiff.

They were all approached for permission to install a one-night-only "bespoke hotel suite" for sleepover prizes. Members of the public can enter a draw to book the suite, and the winner gets a night's stay for two, free of charge.

The Royal Estates politely declined the opportunity to have strangers round for the night (Buckingham Palace has probably had quite enough of that in the past) and others also turned down the idea on security or insurance grounds. However, Eden (third placed in the vote), the London Dungeon, Hastings' Blue Reef Aquarium and Manchester United's Old Trafford stadium – albeit with the pitch strictly out of bounds – were game.

I was sent to test the concept at Eden. The gates were shutting behind the last of the daytime crowds as I arrived for check-in. Munroe, my personal guide for the evening, showed me around the newish Core education centre and the Humid Tropics biome. The scale of the place means that it can happily swallow a lot of people, but as one of the country's top visitor attractions, Eden is inevitably a shared experience. Deserted, it felt quite different; peaceful and atmospheric. There was time and space to stand and stare, to take in the scents and even to taste. Munroe picked leaves and petals, and – night visitor privilege – we munched a fig and dipped our fingers into sticky-sweet flower nectar.

Finally, we reached the Mediterranean biome, my personal biome and "hotel room" for the night. Following a splendid supper in the outlook balcony – Helford oysters, crab and smoked fish platter, lobster and fillet steak "Surf and Turf" with Cornish earlies and asparagus – it was bedtime. The bulbous roof sparkled with a galaxy of reflections from the pathway lights. When I switched them off (and while I hadn't got the television, I did have a neat remote), the real stars flickered hazily beyond.

It was a still night; apparently in a heavy hailstorm, being in the biome is akin to sitting in the centre of the timpani section of an orchestra.

No singing cicadas, unfortunately (in fact, there was a surprising absence of creepy crawlies – I didn't even see any of the little local lizards). Instead, there were just the trickle of a rill and the low Darth Vader-like hush and shush of the ventilation system keeping temperature and humidity stable, circulating comfortably warm air that was heavy with a soporific mixture of herbs and aromatics. Wrapped in a duvet, cocooned in giant bubble-wrap, I fell asleep.

Another thing the biome lacks is curtains; at 4.30am the half light and an early call from babbling resident blackbirds and robins had me awake again. Grey gradually gave way to green and the colour bled back into the vivid red pelargoniums around the bed.

I understand I was the first person ever to sleep the night in the biome; I'm fairly certain I'm the first to wander it in his underpants.

I strolled from Sacramento to Seville, sniffing rosemary and myrtle, crushing a lemon-scented verbena leaf and scrumping dumpy flat peaches, plump nectarines and tomatoes. On a solo world tour, I travelled to more obscure parts: to the Namaqualand Desert north of Cape Town, to the cork oak groves of Portugal.

I had visited the Eden Project several times before, most recently three or four years ago. While the Humid Tropics biome was brimful of lushness, the Med biome was still a bit weedy (in the skinny sense) and sparse; these plants take a while to put on heft and height. Now, it feels fuller – unlike the pathways each morning. I enjoyed every solitary minute, whiling away the dawn in a biome of my own – only leaving as the first of the day's fresh crowds began to fill the car parks again.